My name is Mariam and I am a PhD student in the first year of my studies.

I have been facing several problems performing the MTT but now I would like to ask you. After the incubation time with the MTT solution, is the colour change visible by the human eye? Or should I put it under the microscope to check if any crystals have been formed?

Because usually I see a yellowish colour even after the 2h incubation.

After incubate with MTT solution, there should be no colour changes which can be detected by human eyes.

For my protocol, I'll aspirate the MTT solution after incubate for 4 hours and add in DMSO to dissolve the crystal formed. Dark purple colour can easily detected by human eyes immediately after i add in DMSO into the wells. The colour changes will be detected using microplate reader to read the absorbance. Anyhow, i didn't check the colour of MTT solution during its incubation period as it is light-protected during the incubation period.